The invention relates to a feedback control system for a vehicle clutch, and particularly to an apparatus for automatically operating a vehicle clutch during starting so that torsional variations in the vehicle drive train are attenuated. More particularly, the invention relates to an apparatus having a servo-motor for engaging and disengaging the clutch, measuring sensors for detecting the rotary speeds upstream and downstream of the clutch and the gear stages of a shift gear to provide measured values which are fed to a regulating device which forms from the measured values an output signal which is applied to the servo-motor.
An apparatus of the above-mentioned type is known from German Unexamined Published Application No. 3,004,930. During the starting of the vehicle, by touching a manual switch lever, the clutch is disengaged by a regulating device, and after the engagement of the gear and operation of the accelerator pedal the engine is first of all adjusted to a prescribed engine speed by the regulating device, and then the clutch is engaged again slowly. As soon as the engine speed falls due to an absorption of torque by the clutch, the engagement process is interrupted by the regulating device and is permitted again only when the engine speed has again attained the prescribed value. This regulation process is repeated until approximate equality of rotary speed exists between clutch plate and engine. Only then does the known regulating device permit the clutch to be engaged completely.
It is a disadvantage that in the known clutch regulation system that torsional vibrations which occur in the drive train during starting, and which cause disagreeably pronounced accelerations and vibrations in the vehicle, are not taken into consideration. The reason for this is that the drive train constitutes a component elastic in rotation, which can be tensioned and relaxed like a torsion spring during the starting process as a result of the continuous variations in the clutch moment, whereby jerky accelerations and vibrations can be produced in the vehicle.
Particularly in the case of vehicles having a long drive train and leaf springs as axle suspension means, as for example in the case of commercial vehicles, the drive train possesses a relatively low torsional rigidity, due to which particularly disagreeable vibrations can be produced. The sensitive manuevering of such vehicles is made more difficult by the low torsional rigidity.
According to the present invention, the improved apparatus provides a feedback control system for selectively engaging a clutch of a vehicle having an engine, an engine shaft, and a drive train comprising a clutch assembly including clutch input and output members, a drive shaft, and a wheel assembly. The apparatus includes servo-motor means for engaging and disengaging the clutch members, first measuring sensor means for detecting the angular velocity of the clutch input member, second measuring sensor means for detecting the angular velocity of the drive shaft, and third measuring sensor means for detecting the instantaneous torsional moment transmitted by the drive shaft to the wheel assembly.
The apparatus further includes feedback control means for attenuating vibration in the vehicle drive train, the feedback control means including data processing means for intepreting the parameters detected by the first, second, and third measuring sensor means to monitor torsional vibrations in the drive train, and regulator means to engage selectively the clutch members to regulate thereby the moment of the clutch to cause each of the torsional moment transmitted by the drive shaft and the angular velocity of the engine shaft to approach a constant value so that unwanted torsional vibrations in the vehicle drive train are dynamically monitored and attenuated.
The underlying aim of the present invention is to improve the known apparatus for automatically operating a clutch so that the torsional variations in the drive train are attenuated during starting.
This aim is achieved according to the invention in that measuring sensors are arranged on the drive train leading from the clutch to the driven wheels to detect the angular velocity applied to the clutch on its input side, the angular velocity of the drive shaft on the output side of the clutch, and the torque to be transmitted by the drive train. The above-noted detected values are likewise fed to the feedback control means. The output of the feedback control means influences the servo-motor means via the regulator means so that such a clutch moment (M.sub.2) is applied to the clutch to cause the torsional moment (M.sub.3) and the engine speed (.omega..sub.1) to approach a constant value.
One advantage achieved by the present invention is that the torsional vibrations in the drive train are attenuated by deliberate variations in the clutch moment caused by the improved apparatus, to obtain a jerk-free and uniform acceleration of the vehicle. This improved clutch regulation system further permits a sensitive centimeter-accurate maneuvering of the vehicle. Lastly, a uniform torque curve is also achieved which exhibits no transient maximum values to protect the drive units better.
Further objects, features, and advantages of the present invention will become more apparent from the following description when taken with the accompanying drawing which shows, for purpose of illustration only, an embodiment in accordance with the present invention.